Water-base ink having metallic lustrous color for ballpoint pen

ABSTRACT

Provided is a water based ink having a metallic lustrous color for a ballpoint pen in which a metal powder pigment or aluminum powder and a complementary colorant (pigment or a colored water-insoluble polymer fine particles) are used as a colorant and further in addition to a thickener, a polar solvent and water, particularly a resin emulsion is used in combination to reduce the use amount of the thickener to thereby lower the viscosity. The ink is improved in follow-up property to be able to write continuously, develops a metallic color of a rainbow color on writing paper having a dark color and provides lines having water resistance and weatherability. The ink does not allow the metal powder and the pigment to settle and separate though the viscosity is low.

TECHNICAL FIELD

The present invention relates to a water based ink having a metalliclustrous color for a ballpoint pen in which a metal powder pigment as acolorant and a complementary colorant are used and which can providedrawn lines of a metallic color tone such as gold and silver regardlessof a color tone of writing paper, more specifically to a water based inkhaving a metallic lustrous color for a ballpoint pen which inhibits themetal powder from settling even in storing for a long time and which hasa good follow-up property and can write continuously.

BACKGROUND ART

Aluminum powder, bronze powder and pearl pigments have so far been usedas pigments for obtaining drawn lines of a metallic color tone havingmetallic luster such as gold and silver.

Since bronze powder has a large specific gravity and is susceptible tooxidative discoloration, the addition of the powder having a particlediameter of about several μm which is required for providing the drawnlines with a metallic lustrous tone is liable to cause problems such asseparation by settling, discoloration of the color tone and clogging atthe pen tip, and it is very difficult to use the bronze powder for awater based ink for writing instruments.

Aluminum powder has a smaller specific gravity and a less discoloringproperty as compared with those of bronze powder. However, it has alarger specific gravity as compared with those of conventional pigmentsand has a defect of oxidative discoloration in a high pH area or a lowpH area and a problem that the lines drawn on writing paper having adark color develops only a silver color.

A pearl pigment comprises mica coated on the surface thereof withtitanium oxide and is characterized by that it can provide a metalliclustrous property and a tint of a rainbow color depending on adifference in a refractive index originating in the thickness of thetitanium oxide layer.

However, in order to obtain metallic luster close to that of metalpowder, a particle diameter of 30μ or more is required, and the additionthereof to an ink has caused problems such as separation by settling,clogging at the pen tip and an increase in writing-resistance.

Inks for marking pens using aluminum powder as a metal powder pigmentinclude inks described in Japanese Patent Publication No. Sho 62-37678and Japanese Patent Publication No. Hei 1-56109. Disclosed in JapanesePatent Publication No. Sho 62-37678 is a double coloring ink compositionwhich comprises a metal powder pigment such as aluminum powder, anoil-soluble dye, a resin and a solvent and in which the dye ispenetrated and diffused into the circumference of the drawn lines formedfrom the metal powder pigment to produce an outline effect.

Disclosed in Japanese Patent Publication No. Hei 1-56109 is a metalliclustrous ink for a marking pen which comprises fine metal powder such asaluminum powder subjected to surface treatment, a resin and a solventand which has a good ink follow-up property and does not produce a hardcake by the settling of the metal powder pigment in the ink reservoir ofthe pen barrel.

The ink for a marking pen described above has a problem that since ithas a low viscosity and can not inhibit the aluminum powder fromsettling and separating, a stirring member such as a metal ball is putin the ink reservoir together with the ink, and this marking pen has tobe shaken before writing to disperse once again the settled metal powderpigment, otherwise the good ink follow-up property can not be obtained.

Proposed as well are inks for a ballpoint pen which do not use astirring member such as a metal ball unlike the ink for a marking pendescribed above.

Disclosed in Japanese Patent Application Laid-Open No. Sho 60-186573 isan ink which is characterized by containing a solvent, a thickeningresin soluble in this solvent, a metal powder pigment and a colorpigment at least in each prescribed amount and having a viscosity of aprescribed value or more and which has a metallic color and lessprecipitation of the pigment because of a high viscosity and is suitablefor use in a pressurized ballpoint pen.

Further, disclosed in Japanese Patent Application Laid-Open No. Hei1-210478 is a water based metallic lustrous ink which is characterizedby adding an acetyl alcohol derivative as an additive to a primary inkcomprising a resin, an aluminum paste and water and which prevents staincaused by pin hole in applying.

These conventional techniques have problems on separation by settling,an ink follow-up property and long term stability for water based inksfor ballpoint pens capable of writing under an atmospheric pressure.

Provided in Japanese Patent Application Laid-Open No. Hei 7-118592 is awater based metallic lustrous ink for a ballpoint pen which is providedwith a viscosity of 10,000 to 15,000 cps by a pearl pigment and athickener comprising seed polysaccharides. However, it has such problemsthat the ink follow-up property is reduced because of the high viscosityand the writing-resistance is increased since the particle diameterrequired for providing the metallic luster is too large. Accordingly, itis not satisfactory.

Provided in Japanese Patent Application Laid-Open No. Hei 7-145339 is anink which comprises aluminum powder, natural polysaccharides forthickening, a water-soluble organic solvent and water and in which theviscosity is 100 to 1,500 poise and a ratio of the viscosity at 1 rpm tothe viscosity at 10 rpm is 3.0 or more. However, a problem on theinferior ink follow-up property because of the high viscosity stillremains unsolved, and since a water-soluble dye is used forcomplementing a gold color, a dyeing property of the dye is notsufficient when written on writing paper having a dark color, so thatonly the silver color drawn lines can be obtained. Further, the linesdrawn on writing paper having a pale color have a problem that they areinferior in water resistance and weatherability, so that the drawn linesare discolored. Accordingly, it is not satisfactory.

Provided in Japanese Patent Application Laid-Open No. Hei 6-313142 is awater based metallic lustrous ink comprising aluminum powder, awater-soluble dye, a resin and an inorganic salt, but it has problems ona coloring property on writing paper having a dark color, discolorationof the aluminum powder by oxidation and production of hydrogen andtherefore is not satisfactory as well.

A subject of the present invention is to provide a water based inkhaving a metallic lustrous color for a ballpoint pen which can providedrawn lines having various metallic colors of a rainbow color tone andhas improved water resistance and weatherability and a good follow-upproperty and which can write continuously and is capable of being storedover a long period of time.

DISCLOSURE OF THE INVENTION

The present invention provides a water based ink for a ballpoint pen inwhich a metal powder pigment or aluminum powder as a colorant and acomplementary colorant are used and which is composed of a thickener forpreventing the metal powder from settling and separating, a polarsolvent, water and other controlling agents required for the water basedink for a ballpoint pen and has preferred metallic lustrous color with aresin emulsion blended. Specific embodiments include:

(1) used as a colorant is metal powder which is colored by coating thesurface thereof with a pigment thin film or metal powder whose coloredsurface is further coated with a synthetic resin, and a resin emulsionmay be blended;

(2) used are aluminum powder as a colorant and inorganic and organiccolorants as complementary colorants, and a resin emulsion is used incombination; and

(3) aluminum powder and a colorant obtained by dyeing fine particles ofa water-insoluble polymer with a water-soluble dye are used ascolorants, and in this case, a resin emulsion is not necessary.

A thickener used for the inks in the respective embodiments describedabove is selected from natural polysaccharides, cellulose and syntheticpolymers and is blended in a proportion of 0.1 to 1.5% by weight basedon the weight of the ink. The ink viscosity is controlled to 500 mPa'sor more and less than 8,000 mPa's. When a resin emulsion is used, aresin emulsion and/or a hollow resin emulsion each resin of which has aparticle diameter of 200 nm or more are used in a proportion of 2.0 to10.0% by weight based on the weight of the ink in terms of the weight ofthe resin particles themselves.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiment of the present invention shall be explained in detail.

The colored metal powder pigment used in the first embodiment isprepared by adsorbing or coating a color pigment on the surface of metalpowder making use of a chemical adsorption method or a vacuum depositionmethod. It is clear and excellent in luster such that conventional metalpowders have never been so, and can provide a polychromatic color.

Further, metal powder which is coated with a synthetic resin afteradsorbing the color pigment thereon is more preferred since it can havestrong resistance against corrosive chemicals such as acids and others.

The use amount of the colored metal powder pigment is preferably 4 to15% by weight based on a whole amount of the ink. If the use amount isless than 4% by weight, the drawn lines have a low metallic lustrousproperty, and if the use amount exceeds 12% by weight, the solid contentincreases, and the viscosity of the ink is liable to go up. Further, thefluidity is reduced, and the follow-up property of the ink isdeteriorated, so that inferior writing tends to be likely to take place.

The particles of the colored metal powder pigment have preferably anaverage particle diameter of 10 to 40 μm. The average particle diameterof less than 10 μm reduces the metallic lustrous property of the drawnlines to provide the indistinct drawn lines. The larger average particlediameter produces problems such as separation of the particlesthemselves by settling, clogging at the pen tip part and an increase inthe writing-resistance.

Commercially available colored metal powder pigments include Elgy of avacuum deposition type (manufactured by Oike Ind. Co., Ltd.) and FriendColor of a chemical adsorption type (manufactured by Showa AluminumPowder Co., Ltd.).

The thickener is used for inhibiting the colored metal powder pigmentfrom settling and providing suitable fluidity for an ink for a ballpointpen, and the thickeners having a property that the effect thereof is notreduced when they are used in combination with a colored metal powderpigment and a resin emulsion in a water based ink have to be selected.

The addition amount of the thickener is 0.1 to 1.5% by weight. The smalladdition amount of the thickener is liable to cause settling of thecolored metal powder pigment, and the amount as much as exceeding 1.5%by weight reduces the fluidity of the ink, so that inferior writingtends to be likely to take place due to the inferior follow-up propertyof the ink.

The fluidity can be judged by a viscosity of the ink, and the viscosityvalue at 1 rpm has to be 1,000 mPa's or more in terms of a valuedetermined by means of an E type viscometer which is a conventionalrotational viscometer for inhibiting the colored metal powder pigmentfrom settling. In order to provide this viscosity, the foregoing amountof the thickener has to be added.

Further, if the viscosity value shows 8,000 mPa's or more, the fluidityof the ink is reduced, and the follow-up property of the ink and thefeeding of the ink from the pen tip of the ballpoint pen to a writingpaper are deteriorated. Accordingly, the addition amount of thethickener has to be controlled.

The polar solvent is used in various qualities for a water based ink fora ballpoint pen, for example, the purposes of preventing dry-up of theink at the pen tip and freezing of the ink at a low temperature. To bespecific, a desired water content is 5% or more, preferably 40% or morein terms of a weight percent based on a whole ink composition. Further,water-soluble organic solvents having hygroscopicity such as ethyleneglycol, diethylene glycol, propylene glycol, polyethylene glycol,polypropylene glycol, thiodiglycol, glycerin, diglycerin, 2-pyrrolidone,N-methyl-2-pyrrolidone, dimethylformamide and dimethylimidazolidinoneare used preferably alone or in combination of plural kinds thereof.

The resin emulsion is effective for improving the line coloring propertyof the ink on writing paper having a dark color and inhibiting thecolored metal powder pigment from settling and separating.

The resin particles dispersed in water and a water base solvent, if theyhave an average particle diameter of 200 nm or more, are characterizedby showing a white color owing to effects of reflection and refractionof light, and the larger the particle diameter is, the larger thereflection effect is and the larger the white color-covering propertygrows.

A hollow resin emulsion in which the refraction effect can be expectedto grow large can be expected to have more white color-coveringproperty, and the excellent line coloring property of the ink isobserved.

The presence of the emulsion of a resin having a large particle diameteramong the particles of the colored metal powder pigment having a largeparticle diameter can inhibit the particles of the colored metal powderpigment from adsorbing and coagulating among them and can inhibit theparticles from growing large, and hence the settling-prevention effectcan be produced.

In the second embodiment of the present invention, aluminum powder isused as a pigment for providing the drawn lines with a metallic lustrouscolor.

The flaky aluminum has a high diffusion coefficient, and can provide themetallic lustrous property more clearly. Accordingly, it is particularlypreferred. Aluminum powder is obtained by a stamp method in whichaluminum pieces are pulverized together with an anti-friction agent suchas stearic acid by means of a stamp mill or a ball mill method in whichaluminum powder obtained by an injection method and a lubricant are putin a drum together with suitable steel balls and the drum is rotated topulverize the aluminum pieces.

Usually, the commercially available product can be obtained in the formof an aluminum paste.

An aluminum paste is obtained by pulverizing and abrading aluminumpowder in a ball mill containing a petroleum base solvent (mineralspirit) having a high boiling point and an anti-friction agent such asfatty acid and turning into surface-treated very thin flaky aluminumfine powder, and therefore it has less risk of ignition and explosionand good storage stability and is easy to handle in use.

The use amount of the aluminum powder is preferably 4 to 12% by weightbased on a whole amount of the ink. The use amount of less than 4% byweight reduces the metallic lustrous property of the drawn lines. Incontrast with this, the use amount exceeding 12% by weight increases thesolid content and is liable to raise the viscosity and reduce thefluidity of the ink, so that the follow-up property of the ink isdeteriorated, and inferior writing tends to be likely to take place.

The aluminum powder has preferably an average particle diameter of 5 to25 μm. The average particle diameter of less than 5 μm reduces themetallic lustrous property of the drawn lines to make the drawn linesindistinct. The larger average particle diameter causes problems such asseparation of the particles themselves by settling, clogging at the pentip and an increase in the writing-resistance.

A pigment is used as a complementary colorant for the ink of the presentembodiment.

The complementary colorant is used for toning and developing a colorother than a silver color which is a the ground color of aluminumparticles. The pigment itself is excellent in water resistance andweatherability and can provide semi-permanent drawn lines. Further, ifit is present together with the resin emulsion, the drawn lines canprovide a rainbow color having various color tones regardless of theintensity and the tone of the ground color of writing paper.

Examples of the pigments to be used include inorganic pigments such ascarbon black, titanium white, titanium black, zinc oxide, red ironoxide, chromium oxide, black iron oxide, cobalt blue, alumina white,iron oxide yellow, viridian, zinc sulfide, lithopone, cadmium yellow,vermilion, cadmium red, chrome yellow, molybdate orange, zinc chromate,strontium chromate, white carbon, clay, talc, ultramarine, precipitatedbarium sulfate, baryte powder, calcium carbonate, white lead, Prussianblue, manganese violet, aluminum powder and bronze powder, and organicpigments such as C. I. Pigment Yellow 1, C. I. Pigment Yellow 3, C. I.Pigment Yellow 12, C. I. Pigment Yellow 13, C. I. Pigment Yellow 14, C.I. Pigment Yellow 17, C. I. Pigment Yellow 34, C. I. Pigment Yellow 55,C. I. Pigment Yellow 74, C. I. Pigment Yellow 83, C. I. Pigment Yellow95, C. I. Pigment Yellow 166, C. I. Pigment Yellow 167, C. I. PigmentRed 5, C. I. Pigment Red 22, C. I. Pigment Red 38, C. I. Pigment Red 48,C. I. Pigment Red 49, C. I. Pigment Red 53, C. I. Pigment Red 57, C. I.Pigment Red 81, C. I. Pigment Red 104, C. I. Pigment Red 146, C. I.Pigment Red 245, C. I. Pigment Blue 1, C. I. Pigment Blue 15, C. I.Pigment Blue 27, C. I. Pigment Violet 1, C. I. Pigment Violet 3, C. I.Pigment Violet 19, C. I. Pigment Violet 23, C. I. Pigment Violet 50, C.I. Pigment Orange 5, C. I. Pigment Orange 13, C. I. Pigment Orange 16and C. I. Pigment Green 7. They are used alone or in combination ofplural kinds thereof.

The thickener is used for inhibiting the aluminum powder from settlingand providing suitable fluidity for an ink for a ballpoint pen, and thethickeners having a property that the effect thereof is not reduced whenthey are used in combination with aluminum powder, a resin emulsion anda complementary color pigment in a water based ink have to be selected.

The addition amount of the thickener is 0.1 to 1.5% by weight based on awhole ink. The small addition amount of the thickener is liable to causesettling of the aluminum powder particles, and the amount as much asexceeding 1.5% by weight reduces the fluidity of the ink, so thatinferior writing tends to be likely to take place due to the inferiorfollow-up property of the ink.

The fluidity can be judged by a viscosity of the ink, and the viscosityvalue at 1 rpm has to be 500 mPa's or more in terms of a valuedetermined by means of an E type viscometer which is a conventionalrotational viscometer for inhibiting the aluminum powder from settling.In order to provide this viscosity, the foregoing amount of thethickener has to be added.

Further, if the viscosity value shows 8,000 mPa's or more, the fluidityof the ink is reduced, and the follow-up property of the ink and thefeeding of the ink from the pent tip of the ballpoint pen to writingpaper are deteriorated. Accordingly, the addition amount of thethickener has to be controlled.

The polar solvent is used in various qualities for a water based ink fora ballpoint pen, for example, the purposes of preventing dry-up of theink at the pen tip and freezing of the ink at a low temperature.

To be specific, a desired water content is 5% or more, preferably 40% ormore in terms of a weight percent based on a whole ink composition.Further, water-soluble organic solvents having hygroscopicity such asethylene glycol, diethylene glycol, propylene glycol, polyethyleneglycol, polypropylene glycol, thiodiglycol, glycerin, diglycerin,2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide anddimethylimidazolidinone are used preferably alone or in combination ofplural kinds thereof.

The resin emulsion is required for improving the line coloring propertyof the ink on writing paper having a dark color and inhibiting thealuminum powder from settling and separating.

The resin particles dispersed in water and a water base solvent, if theyhave an average particle diameter of 200 nm or more, are characterizedby showing a white color owing to effects of reflection and refractionof light, and the larger the particle diameter is, the larger thereflection effect is and the larger the white color-covering propertygrows.

A hollow resin emulsion in which the refraction effect can be expectedto grow large can be expected to have more white color-coveringproperty, and the excellent line coloring property of the ink isobserved.

The presence of the emulsion of a resin having a large particle diameteramong the particles of the aluminum powder having a large particlediameter can inhibit the particles of the aluminum powder from adsorbingand coagulating among them and can inhibit the particles from growinglarge, and hence the settling-prevention effect can be produced.

The third embodiment of the present invention is an ink having ametallic lustrous color containing a colorant obtained by dyeingwater-insoluble polymer fine particles with a water-soluble dye andaluminum powder.

The aluminum powder used for the ink of the present embodiment has anaverage particle diameter falling in a range of 1 to 50 μm. A largerdiameter makes the ink instable with the lapse of time to causeseparation and is liable to bring about coagulation. On the other hand,a smaller diameter causes the metallic lustrous property to be short andmakes the color tone dull, so that such diameters are not suitable. Thediameter is preferably 5 to 30 μm.

The average particle diameter of less than 5 μm reduces the metalliclustrous property of the drawn lines to make the drawn lines indistinct.If the average particle diameter is as large as over 30 μm, particularlyover 50 μm, caused are problems such as separation of the particlesthemselves by settling, clogging at the pen tip and an increase in thewriting-resistance.

The use amount of the aluminum powder is preferably 4 to 12% by weightbased on a whole amount of the ink.

The use amount of 4% by weight or less reduces the metallic lustrousproperty of the drawn lines, and the use amount exceeding 12% by weightis liable to raise the viscosity and reduces the fluidity of the ink, sothat the follow-up property of the ink is deteriorated, and inferiorwriting tends to be likely to take place.

Commercially available aluminum paste can be used for the aluminumpowder.

The colorant obtained by dyeing water-insoluble polymer fine particleswith a water-soluble dye has an average particle diameter falling in arange of 0.1 to 1.0 μm.

When conventional pigments are used as the colorant in the present waterbased ink, the amount of the solid contained in the ink is small, andthe colorant settles down and separates, so that the ink is lacking instability.

When conventional dyes (acid dyes, basic dyes and direct dyes) are used,the drawn lines are inferior in weatherability and water resistance.Further, they have a defect that when written on writing paper having adark color, the coloring property of the dye is lost, and only thesilver color of aluminum is shown. Accordingly, they are not suitable.Also when the water-insoluble polymer fine particles are used, theconsistency of the visual hue of the ink with the hue of the drawn linesis deteriorated when the average particle diameter is small, and if adifference between the hues is large, the ink becomes instable with thelapse of time, and phase separation is liable to take place.Accordingly, such a diameter is not suitable. The average particlediameter is preferably 0.2 to 0.6 μm.

The present water based ink is prevented from separation and colorparting by controlling the sum of the water-insoluble polymer fineparticles as a colorant and the aluminum powder to 5 to 60% by weight.If the sum is less than this range, separation and color parting takeplace, and if it exceeds this range, coagulation is caused. Accordingly,both are not suitable.

The sum is preferably 15 to 45% by weight, more preferably 20 to 35% byweight.

Water is used as a principal solvent for the present water based ink,and all solvents which have polar groups and are miscible with water canbe used as the polar solvent. There can be used, for example, ethyleneglycol, diethylene glycol, triethylene glycol, polyethylene glycol,propylene glycol, ethylene glycol monomethyl ether, glycerin,pyrrolidone and triethanolamine.

The use amount thereof is 5 to 50% by weight, preferably 10 to 30% byweight based on the composition.

The addition of the thickener to the present water based ink provides anink having more dispersion stability.

The use amount of the thickener falls preferably in a range of 0.1 to1.5% by weight based on a whole ink.

The small addition amount of the thickener is liable to cause settlingof the aluminum powder particles, and the amount as much as exceeding1.5% by weight reduces the fluidity of the ink, so that inferior writingtends to be likely to take place due to the inferior follow-up propertyof the ink.

The fluidity can be judged by a viscosity of the ink, and the viscosityvalue at 1 rpm has to be 500 mPa's or more in terms of a valuedetermined by means of an E type viscometer which is a conventionalrotational viscometer for inhibiting the aluminum powder from settling.In order to provide this viscosity, the foregoing amount of thethickener has to be added.

Further, if the viscosity value shows 6,000 mPa's or more, the fluidityof the ink is reduced, and the follow-up property of the ink isdeteriorated. Accordingly, the addition amount of the thickener has tobe controlled.

Next, the components used in the respective embodiments of the presentinvention shall be explained.

The commercially available aluminum pastes which are suited to thepresent invention include brand names Super Fine No. 22000WN and SuperFine No. 18000 manufactured by Daiwa Metal Ind. Co., Ltd.; brand namesWB0230 and WB1200 manufactured by Toyo Aluminum K.K.; brand nameSAP-1110-W manufactured by Showa Denko K.K.; brand nameSTAPAHYDROLAC-300-SUPER manufactured by Eckart Co., Ltd.; and brand nameAW-808C manufactured by Asahi Chemical Industry Co., Ltd.

The aluminum powder includes brand names AA12, No. 900 and No. 18000manufactured by Fukuda Metal Foil Ind. Co., Ltd.

The thickener used in the present invention includes, to be specific,natural polysaccharides, i.e. seed polysaccharides such as guar gum,locust bean gum, galactomannan, pectin and derivatives thereof, psylliumseed gum and tamarind gum; biological base gums such as xanthan gum,rheozan gum, rhamsan gum, welan gum and gellan gum; sea weedpolysaccharides such as carrageenan, alginic acid and derivativesthereof; resin polysaccharides such as trangacanth gum; cellulose andderivatives thereof such as ethyl cellulose, methyl cellulose,hydroxymethyl cellulose and carboxymethyl cellulose; and syntheticpolymers such as polyacrylic acid and cross-linking type copolymersthereof, polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone andderivatives thereof, polyvinyl methyl ether and derivatives thereof, andpolyacrylamide.

In particular, the biological base gums are characterized by a strongviscosity-providing effect and physical properties which are stable evenafter storage over a long period of time but tend to have strongproperties for propagating miscellaneous fungi and coagulating finepowder pigments.

Polyacrylic acid and cross-linking type copolymers thereof arecharacterized by stability against coagulation of fine powder pigmentsand propagation of miscellaneous fungi but tend to be inferior in aviscosity-providing property to natural polysaccharides.

At least one thickener selected from the thickeners described above canbe used depending on the addition amounts and the kinds of the coloredmetal powder pigment, the aluminum powder and the complementary colorantof the ink components.

For example, if the aluminum powder is eluted in water in the form ofions by virtue of trace amounts of electrolytes contained in the ink,the water-soluble resins used for dispersing and stabilizing the pigmentand for the thickener are gelatinized, hydrolyzed or partiallyinsolubilized by the action of the aluminum ions, so that the ink tendsto increase in viscosity or separate and coagulate.

The thickeners having functional groups capable of inactivating theeluted aluminum ion by an ionic bond, for example, xanthan gum andrheozan gum having glucuronic acid on side chains, cationizedderivatives of guar gum and locust bean gum, and polyacrylic acid havingcarboxylic acid can maintain a long term storage stability in a waterbased ink containing aluminum powder and tend to be liable to preventdeterioration of the ink.

The use amount of the thickener is preferably 0.1 to 1.5% by weight. Theuse amount is varied depending on the kind of the thickener. It ispreferably 0.1 to 0.8% by weight in natural polysaccharides andpreferably 0.5 to 1.5% by weight in synthetic polymers.

Examples of the resin emulsion include brand names Acronal YJ-1556D andAcronal S-400 manufactured by Mitsubishi Chemicals Corporation; brandnames Voncoat AB-735 and AN-865 manufactured by Dainippon Ink andChemicals Inc.; brand names Microgel E-3101 and Microgel MPE-13manufactured by Nippon Paint Co., Ltd.; and brand names STADEX-SC-041-Sand STADEX-SC-051-S manufactured by Japan Synthetic Rubber Co., Ltd.

The hollow resin emulsion includes brand names Ropaque OP-62 and RopaqueOP-84J manufactured by Rohm & Haas Co., Ltd.; and a brand name NipolMH-505 manufactured by Nippon Zeon Co., Ltd.

The addition amount of the resin emulsion is preferably 2.0 to 10.0% byweight in terms of the weight of the resin particles themselves. The useamount of less than 2.0% by weight can not cover the ground color ofwriting paper having a dark color and does not provide a good coloringproperty of a metallic tone rainbow color, so that the drawn linesassume an aluminum color or the metal particles can not be inhibitedfrom coagulating and tend to settle down.

Further, the use amount exceeding 10% by weight intensifies theinteraction with the thickener to reduce the fluidity of the ink inspite of a small viscosity value and tends to deteriorate the writingproperty. Accordingly, the use amount is preferably 2.0 to 10.0% byweight in terms of the weight of the resin particles themselves.

Added, if necessary, as other adjusting agents are pH adjusting agentssuch as ammonia, urea, monoethanolamine, diethanolamine,triethanolamine, alkaline metal salts of carbonic acid and phosphoricacid such as sodium tripolyphosphate and sodium carbonate, andhydroxides of alkaline metals such as sodium hydroxide; preservatives orfungicides such as phenol, sodium omadine, sodium pentachlorophenol,1,2-benzisothiazoline-3-one,2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine, alkaline metal salts ofbenzoic acid, sorbic acid and dehydroacetic acid such as sodiumbenzoate, and benzimidazole base compounds; rust preventives such asbenzotriazole, dicyclohexylammonium nitrite, diisopropylammonium nitriteand tolyltriazole; surfactants such as derivatives of polyoxyethylene,polyoxypropylene or polyoxyethylenepolyoxypropylene such aspolyoxyethylene lauryl ether, derivatives of glycerin, diglycerin orpolyglycerin such as tetraglycerin distearate, sorbitan derivatives suchas sorbitan monooleate, fatty acid alkali salts, nonionic surfactants,and compounds having fluorinated alkyl groups such asperfluoroalkylphosphoric acid esters; and lubricants and wetting agentssuch as polyether-modified silicone including polyethylene glycoladducts of dimethylpolysiloxane.

These surfactants given as examples of lubricants and wetting agentshave a function to disperse and stabilize a pigment, aluminum powder andmetal powder pigment particles, but preferably used as dispersants areanionic surfactants such as alkyl sulfonic acid salts of higher fattyacid amide and alkylarylsulfonic acid salts, and water-soluble polymerssuch as polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid,polyacrylic acid copolymers, acrylic-methacrylic acid base resins,styrene-acryl base resins, maleic acid resins and styrene-maleic acidbase resins.

Various methods for producing inks which have so far been known can beemployed for producing the water based ink having a material lustrouscolor for a ballpoint pen of the present invention.

It can readily be obtained by, for example, blending the respectivecomponents described above and mixing and stirring them by means of astirrer such as a dissolver or mixing and crushing them by means of aball mill or three rolls and then removing coarse particles, undissolvedmaterials and admixed solid substances out of the pigment particles andaluminum powder particles by centrifugation and filtration.

The present invention shall more specifically be explained below withreference to examples, but the present invention shall not be restrictedto these examples.

The inks obtained in the following examples and comparative exampleswere tested by the following testing methods.

(1) Measurement of average particle diameter (μm)

The average particle diameter (μm) was determined by means of NICOMP 370(manufactured by Nozaki & Co., Ltd., particle diameter measuringapparatus) using a photon correlation method within a week afterpreparing the inks.

(2) Measurement of average particle diameter (μm) with lapse of time

After leaving standing at room temperature for six months afterpreparing the inks, the particle diameter was determined by the samemethod as that in (1).

(3) Measurement of viscosity value

The viscosity value at 1 rpm was determined at 25° C. by means of an EMDtype viscometer (manufactured by Toki Sangyo Co., Ltd.) within a weekafter preparing the inks.

(4) Measurement of viscosity value with lapse of time

After leaving standing at room temperature for six months afterpreparing the inks, the viscosity value at 1 rpm was determined by thesame method as that in (3).

(5) Coloring property of ink

The ink was filled into a refill comprising a polypropylene-made inkreservoir having a inner diameter of 3.5 mm and a length of 100 mm andhaving no feed, and a stainless steel-made pen tip having a balldiameter of 0.7 mm to prepare a ballpoint pen for evaluation.

This ballpoint pen for evaluation was used to write on a Xerox M paper(absorbent paper), a black coat paper (non-absorbent paper) and a blackdrawing paper (absorbent paper: New Color No. 418 manufactured byShikoku Paper Co., Ltd.) respectively to observe the coloring propertyof the drawn lines thereof with eyes.

The evaluation criteria is based on the following 5 grade evaluation:

◯: coloring of colored metallic color

: coloring of a little colored metallic color with a large reduction incoloring

.increment.: coloring of metallic color with partial marked silver color

▴: coloring of almost only silver color

X: coloring of only metallic silver color

(6) Follow-up property of ink

A ballpoint pen for tests was used for quickly writing spirals with ahand, and the presence of starving and splitting in the resulting lineswas observed with eyes:

⊚: not present at all

◯: slightly present

.increment.: a little present

X: present very much

(7) Metallic lustrous property of ink

The ink was applied on writing paper in a fixed film thickness at roomtemperature, and the metallic lustrous property of the ink was evaluatedaccording to the following criteria:

◯: distinct metallic lustrous property observed

.increment.: a little inferior in metallic lustrous property

X: no metallic lustrous property observed

(8) Stability of ink with lapse of time

The ink put in a glass sample bottle in a tightly sealed state was leftstanding under a condition of 50° C. for a month to observe a phaseseparation of the aluminum powder part of the ink from the other parts,and this was evaluated in terms of a stability of the ink with lapse oftime according to the following criteria:

◯: little difference from initial stage observed

.increment.: a little phase separation observed but usable

X: phase separation produced to such an extent as unusable

EXAMPLE 1

    ______________________________________                                        Friend Color (F350RG 10.0   parts by weight                                   manufactured by Showa Aluminum                                                Powder Co., Ltd.: colored                                                     metallic powder pigment content                                               40% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Xanthan gum          0.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Purified water       69.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink for a ballpoint pen.

EXAMPLE 2

    ______________________________________                                        Friend Color (F350RG 7.0    parts by weight                                   manufactured by Showa Aluminum                                                Powder Co., Ltd.: colored                                                     metallic powder pigment content                                               40% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Xanthan gum          0.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Hollow resin emulsion                                                                              10.0   parts by weight                                   (Ropaque OP-84J manufactured                                                  by Rohm & Haas Co., Ltd.:                                                     resin particle content 42.5                                                   % by weight, average particle                                                 diameter 550 nm)                                                              Purified water       62.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink for a ballpoint pen.

EXAMPLE 3

    ______________________________________                                        Friend Color (F350GR 10.0   parts by weight                                   manufactured by Showa Aluminum                                                Powder Co., Ltd.: colored                                                     metallic powder pigment content                                               40% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Locust bean gum      0.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Purified water       69.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink for a ballpoint pen.

EXAMPLE 4

    ______________________________________                                        Friend Color (F350BL 10.0   parts by weight                                   manufactured by Showa Aluminum                                                Powder Co., Ltd.: colored                                                     metallic powder pigment content                                               40% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Hiviswako 105        0.8    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Purified water       68.7   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink for a ballpoint pen.

Comparative Example 1

A colored metallic powder pigment and a resin emulsion are not used:

    ______________________________________                                        Aluminum paste (WB0230                                                                             10.0   parts by weight                                   manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Xanthan gum          0.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Purified water       69.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink.

Comparative Example 2

A pigment is used but a resin emulsion is not blended:

    ______________________________________                                        Aluminum paste (WB0230                                                                              8.0    parts by weight                                  manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol      20.0   parts by weight                                  Xanthane gum          0.5    parts by weight                                  Potassium oleate      0.5    parts by weight                                  Lacqutimine Color (Golden Yellow                                                                    15.0   parts by weight                                  FL2R Conc. manufactured by                                                    Dainichiseika Color & Chemicals MFG. Co.,                                     Ltd.)                                                                         Purified water        56.0   parts by weight                                  ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink.

Comparative Example 3

    ______________________________________                                        Aluminum paste (WB0230                                                                              8.0    parts by weight                                  manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol      20.0   parts by weight                                  Xanthan gum           0.5    parts by weight                                  Potassium oleate      0.5    parts by weight                                  Lacqutimine Color (Light Green                                                                      15.0   parts by weight                                  FLK Conc. manufactured by                                                     Dainichiseika Color & Chemicals MFG. Co.,                                     Ltd.)                                                                         Purified water        56.0   parts by weight                                  ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink.

Test results of the inks obtained in Examples 1 to 4 and ComparativeExamples 1 to 3 are shown in Table 1 and Table 2.

                  TABLE 1                                                         ______________________________________                                                  Average particle                                                                          Viscosity value                                                   diameter (μm)                                                                          (mPa'a)                                                                 After 6           After 6                                               Initial                                                                             months    Initial months                                      ______________________________________                                        Example-1   35.8    40.2      1800  2200                                      Example-2   30.3    32.5      1660  1800                                      Example-3   37.4    40.0      2550  3210                                      Example-4   36.5    42.5      1400  1600                                      Comparative 16.0    38.5      1800  3750                                      Example-1                                                                     Comparative 18.0    42.5      2450  2800                                      Example-2                                                                     Comparative 19.0    45.0      2800  4230                                      Example-3                                                                     ______________________________________                                    

Average particle diameter (μm) and viscosity value (mPa'a):

It can clearly be found from the results of this table that the inksobtained in the examples have less variation in coagulation of thealuminum powder particles and the thickening property with the lapse oftime and are stable.

                  TABLE 2                                                         ______________________________________                                               Ink coloring property                                                                Black                                                                  Xerox  drawing Coat    Ink follow-up property                                 M paper                                                                              paper   paper   Starving                                                                             Splitting                                ______________________________________                                        Example-1                                                                              ◯                                                                          Δ ◯                                                                       ◯                                                                        ◯                          Example-2                                                                              ◯                                                                          ◯                                                                         ◯                                                                       ⊚                                                                     ⊚                       Example-3                                                                              ◯                                                                          Δ ◯                                                                       ◯                                                                        ◯                          Example-4                                                                              ◯                                                                          Δ ◯                                                                       ◯                                                                        ⊚                       Comparative                                                                            ▴                                                                       ▴                                                                      ▴                                                                    ◯                                                                        Δ                                Example-1                                                                     Comparative                                                                            Δ  ▴                                                                      Δ                                                                             ◯                                                                        Δ                                Example-2                                                                     Comparative                                                                            ▴                                                                       ▴                                                                      ▴                                                                    Δ                                                                              Δ                                Example-3                                                                     ______________________________________                                    

Ink coloring property and ink follow-up property

It can be judged from the results of this table that the inks obtainedin the examples are excellent in an ink coloring property and an inkfollow-up property as compared with the inks prepared in the comparativeexamples.

EXAMPLE 5

    ______________________________________                                        Aluminum paste (WB0230                                                                             10.0   parts by weight                                   manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Xanthan gum          0.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Hollow resin emulsion                                                                              10.0   parts by weight                                   (Ropaque OP-84J manufactured                                                  by Rohm & Haas Co., Ltd.:                                                     resin particle content 42.5                                                   % by weight, average particle                                                 diameter 550 nm)                                                              Purified water       59.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a silver color water based ink for a ballpoint pen.

EXAMPLE 6

    ______________________________________                                        Aluminum paste (WB0230                                                                              8.0    parts by weight                                  manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol      20.0   parts by weight                                  Xanthan gum           0.5    parts by weight                                  Potassium oleate      0.5    parts by weight                                  Complementary color pigment                                                                         15.0   parts by weight                                  (Lacqutimine Color Golden Yellow                                              FL2R Conc. manufactured by                                                    Dainichiseika Color & Chemicals MFG. Co.,                                     Ltd.)                                                                         Hollow resin emulsion 10.0   parts by weight                                  (Ropaque OP-84J manufactured                                                  by Rohm & Haas Co., Ltd.:                                                     resin particle content 42.5                                                   % by weight, average particle                                                 diameter 550 nm)                                                              Purified water        46.0   parts by weight                                  ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a golden color water based ink for a ballpoint pen.

EXAMPLE 7

    ______________________________________                                        Aluminum paste (WB0230                                                                             8.0    parts by weight                                   manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Locust bean gum      0.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Complementary color pigment                                                                        15.0   parts by weight                                   (Lacqutimine Color Blue FL2B                                                  Conc. manufactured by Dainichiseika                                           Color & Chemicals MFG. Co., Ltd.)                                             Hollow resin emulsion                                                                              10.0   parts by weight                                   (Ropaque OP-84J manufactured                                                  by Rohm & Haas Co., Ltd.:                                                     resin particle content 42.5                                                   % by weight, average particle                                                 diameter 550 nm)                                                              Purified water       46.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a blue metallic color water based ink for a ballpoint pen.

EXAMPLE 8

    ______________________________________                                        Aluminum paste (WB0230                                                                             8.0    parts by weight                                   manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol     15.0   parts by weight                                   Locust bean gum      0.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Complementary color pigment                                                                        15.0   parts by weight                                   (Lacqutimine Color Green FLB                                                  Conc. manufactured by Dainichiseika                                           Color & Chemicals MFG. Co., Ltd.)                                             Hollow resin emulsion                                                                              10.0   parts by weight                                   (Ropaque OP-84J manufactured                                                  by Rohm & Haas Co., Ltd.:                                                     resin particle content 42.5                                                   % by weight average particle                                                  diameter 550 nm)                                                              Purified water       51.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a green metallic color water based ink for a ballpoint pen.

Comparative Example 4

A resin emulsion has an average particle diameter of 200 nm or less andthe blending amount is larger than 10.0% by weight:

    ______________________________________                                        Aluminum paste (WB0230                                                                              8.0    parts by weight                                  manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol      20.0   parts by weight                                  Xanthan gum           0.5    parts by weight                                  Potassium oleate      0.5    parts by weight                                  Complementary color pigment                                                                         15.0   parts by weight                                  (Lacqutimine Color Golden Yellow                                              FL2R Conc. manufactured by                                                    Dainichiseika Color & Chemicals MFG. Co.,                                     Ltd.)                                                                         Hollow resin emulsion 15.0   parts by weight                                  (Joncryl J-780 manufactured                                                   by Johnson Polymer Co., Ltd.:                                                 resin particle content 42%                                                    by weight average particle                                                    diameter 100 nm)                                                              Purified water        41.0   parts by weight                                  ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink.

Comparative Example 5

A complementary color pigment is not used and a dye is used:

    ______________________________________                                        Aluminum paste (WB0230                                                                             8.0    parts by weight                                   manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Xanthan gum          0.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Dye (Water Blue 105  5.0    parts by weight                                   manufactured by Orient                                                        Chemical Ind. Ltd.)                                                           Hollow resin emulsion                                                                              10.0   parts by weight                                   (Ropaque OP-84J manufactured                                                  by Rohm & Haas Co., Ltd.:                                                     resin particle content 42.5                                                   % by weight, average particle                                                 diameter 550 nm)                                                              Purified water       56.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink.

Comparative Example 6

A complementary color pigment and a resin emulsion are not blended:

    ______________________________________                                        Aluminum paste (WB0230                                                                             10.0   parts by weight                                   manufactured by Toyo Aluminum                                                 K.K.: aluminum powder content                                                 68% by weight)                                                                Propylene glycol     20.0   parts by weight                                   Xanthan gum          1.5    parts by weight                                   Potassium oleate     0.5    parts by weight                                   Purified water       68.0   parts by weight                                   ______________________________________                                    

The compounds described above were filtered after stirring to therebyobtain a water based ink.

Test results of the inks obtained in Examples 5 to 8 and ComparativeExamples 4 to 6 are shown in Table 3 and Table 4 together with theresults obtained in Comparative Examples 1 to 2.

                  TABLE 3                                                         ______________________________________                                                 Average particle                                                                          Viscosity value                                                   diameter (μm)                                                                          (mPa'a)                                                                 After 6           After 6                                               Initial                                                                             months    Initial months                                       ______________________________________                                        Example-5  15.2    18.0      2800  3200                                       Example-6  14.8    18.0      2300  2560                                       Example-7  18.0    22.0      3050  3470                                       Example-8  20.5    22.5      4400  5600                                       Comparative                                                                              16.0    38.5      1800  3750                                       Example-1                                                                     Comparative                                                                              18.0    42.5      2450  2800                                       Example-2                                                                     Comparative                                                                              19.0    45.0      3800  6120                                       Example-4                                                                     Comparative                                                                              21.0    55.8      1500  1750                                       Example-5                                                                     Comparative                                                                              21.0    55.8      9500  16000                                      Example-6                                                                     ______________________________________                                    

It is apparent from the results of the table described above that theinks obtained in the examples have less variation in coagulation of thealuminum powder particles and the thickening property with the lapse oftime and are stable.

                  TABLE 4                                                         ______________________________________                                               Ink coloring property                                                                Black                                                                  Xerox  drawing Coat    Ink follow-up property                                 M paper                                                                              paper   paper   Starving                                                                             Splitting                                ______________________________________                                        Example-5                                                                              ▴                                                                       ▴                                                                      ▴                                                                    ⊚                                                                     ⊚                       Example-6                                                                              ◯                                                                          Δ ◯                                                                       ⊚                                                                     ⊚                       Example-7                                                                              ◯                                                                          ◯                                                                         ◯                                                                       ⊚                                                                     ◯                          Example-8                                                                              ◯                                                                          ◯                                                                         ◯                                                                       ◯                                                                        Δ                                Comparative                                                                            ▴                                                                       ▴                                                                      ▴                                                                    ◯                                                                        Δ                                Example-1                                                                     Comparative                                                                            Δ  ▴                                                                      Δ                                                                             ◯                                                                        Δ                                Example-2                                                                     Comparative                                                                            ▴                                                                       ▴                                                                      ▴                                                                    Δ                                                                              Δ                                Example-4                                                                     Comparative                                                                            ▴                                                                       ▴                                                                      ▴                                                                    ◯                                                                        ◯                          Example-5                                                                     Comparative                                                                            ◯                                                                          Δ ◯                                                                       X      X                                      Example-6                                                                     ______________________________________                                    

It can be judged from the results of the table described above that theinks obtained in the examples are excellent in an ink coloring propertyand an ink follow-up property.

EXAMPLE 9

    ______________________________________                                        Water-insoluble polymer                                                                             40.0   parts by weight                                  fine particles (Lumikol                                                       NKW-2117P manufactured by                                                     Nippon Fluorescent Chemical Co., Ltd.)                                        Aluminum paste (AW808C                                                                              5.0    parts by weight                                  manufactured by Asahi                                                         Chemical Industry Co., Ltd.)                                                  Glycerin              20.0   parts by weight                                  Water                 33.2   parts by weight                                  Benzotriazole         0.5    part by weight                                   Triethanolamine       1.0    part by weight                                   Kelzan (thickener:    0.3    part by weight                                   manufactured by Sansho                                                        Co., Ltd.)                                                                    ______________________________________                                    

The compounds described above were blended and filtered after stirringat ambient temperature for 2 hours to thereby obtain a pink color inkhaving a metallic lustrous property.

EXAMPLE 10

    ______________________________________                                        Water-insoluble polymer                                                                            40.0   parts by weight                                   fine particles (Lumikol                                                       NKW-2103P manufactured by                                                     Nippon Fluorescent Chemical                                                   Co., Ltd.)                                                                    Aluminum paste (Super Fine                                                                         8.0    parts by weight                                   No. 22000WN manufactured by                                                   Daiwa Metal powder Ind. Co., Ltd.)                                            Glycerin             20.0   parts by weight                                   Water                30.3   parts by weight                                   Benzotriazole        0.5    part by weight                                    Triethanolamine      0.8    part by weight                                    Rheogic 252L (thickener:                                                                           0.4    part by weight                                    manufactured by Wako Pure                                                     Chemical Industries, Ltd.)                                                    ______________________________________                                    

The compounds described above were blended and filtered after stirringat ambient temperature for 2 hours to thereby obtain a red ink having ametallic lustrous property.

EXAMPLE 11

    ______________________________________                                        Water-insoluble polymer                                                                            45.0   parts by weight                                   fine particles (Lumikol                                                       NKW-2104P manufactured by                                                     Nippon Fluorescent Chemical                                                   Co., Ltd.)                                                                    Aluminum paste (SAP-1110-W                                                                         5.0    parts by weight                                   manufactured by Showa Denko                                                   K.K.)                                                                         Glycerin             20.0   parts by weight                                   Water                28.2   parts by weight                                   Benzotriazole        0.5    part by weight                                    Triethanolamine      1.0    part by weight                                    Hiviswako #105 (thickener:                                                                         0.3    part by weight                                    manufactured by Wako Pure                                                     Chemicals Industries, Ltd.)                                                   ______________________________________                                    

The compounds described above were blended and filtered after stirringat ambient temperature for 2 hours to thereby obtain an orange color inkhaving a metallic lustrous property.

The inks obtained in Examples 9 to 11 were tested for a metalliclustrous property and stability with the lapse of time. The resultsthereof are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                                        Example                                                                       9       10    11                                              ______________________________________                                        Metallic lustrous property of ink                                                               ◯                                                                           ◯                                                                       ◯                               Stability with lapse of time                                                                    ◯                                                                           ◯                                                                       Δ                                     ______________________________________                                    

INDUSTRIAL APPLICABILITY

The water based pigment ink having a metallic lustrous color for aballpoint pen of the present invention is excellent in a long termstorage stability owing to the presence of the colored metallic powderpigment and covers the ground color of writing paper, so that it canprovide drawn lines having a metallic lustrous color which is excellentin coloring on any writing paper. It can be used for stamps and printersas well as ballpoint pens.

What is claimed is:
 1. A water based ink having a metallic lustrouscolor for a ballpoint pen comprising at least a metal powder pigment,said metal powder pigment having surfaces wherein color pigment isabsorbed or coated on said surfaces, a thickener, water and a polarsolvent, wherein the ink has a viscosity of 1,000 mPa's or more and lessthan 8,000 mPa's.
 2. The water based ink having a metallic lustrouscolor for a ballpoint pen as described in claim 1, wherein said metalpowder pigment in which metal powder surfaces are subjected to coloringtreatment are coated with a synthetic resin.
 3. The water based inkhaving a metallic lustrous color for a ballpoint pen as described inclaim 1, further comprising blending a resin emulsion and/or a hollowresin emulsion each resin of which has a particle diameter of 200 nm ormore.
 4. The water based ink having a metallic lustrous color for aballpoint pen as described in claim 1, wherein the blending amount ofthe thickener is 0.1 to 1.5% by weight.
 5. The water based ink having ametallic lustrous color for a ballpoint pen as described in claim 1,wherein the thickener is selected from at least one of the groupconsisting of xanthan gum and rheozan gum having glucuronic acid on sidechains, cationized derivatives of guar gum and locust bean gum, andpolyacrylic acid having carboxylic acid.
 6. The water based ink having ametallic lustrous color for a ballpoint pen as described in claim 1,wherein the polar solvent is selected from at least one of the groupconsisting of ethylene glycol, diethylene glycol, propylene glycol,polyethylene glycol, polypropylene glycol, thiodiglycol, glycerin,diglycerin, 2-pyrrolidone, N-methyl-2-pyrrolidone, dimethylformamide anddimethylimidazolidinone.
 7. The water based ink having a metalliclustrous color for a ballpoint pen as described in claim 1, whereinwater is contained in a proportion of 40% or more in terms of a weightpercent based on a whole ink composition.
 8. The water based ink havinga metallic lustrous color for a ballpoint pen as described in claim 3,wherein the addition amount of the resin emulsion and/or the hollowresin emulsion is 2.0 to 10.0% by weight in terms of the weight of theresin particles themselves.
 9. A water based ink having a metalliclustrous color for a ballpoint pen which comprises a colorant comprisingwater-insoluble polymer fine particles dyed with a water soluble dye,aluminum powder and a thickener and which is dispersed in a polarsolvent, wherein the ink has a viscosity of 500 mPa's or more and lessthan 6,000 mPa's.
 10. The water based ink having a metallic lustrouscolor for a ballpoint pen as described in claim 9, wherein the coloranthas an average particle diameter falling in a range of 0.1 to 1.0 μm.11. The water based ink having a metallic lustrous color for a ballpointpen as described in claim 9, wherein the aluminum powder has an averageparticle diameter falling in a range of 5 to 30 μm.
 12. The water basedink having a metallic lustrous color for a ballpoint pen as described inclaim 9, wherein the sum of content of the colorant and the aluminumpowder accounts for 5 to 60% by weight.
 13. The water based ink having ametallic lustrous color for a ballpoint pen as described in claim 9,wherein the blending amount of the thickener is 0.1 to 1.5% by weight.14. The water based ink having a metallic lustrous color for a ballpointpen as described in claim 9, wherein the thickener is selected from atleast one of the group consisting of xanthan gum and rheozan gum havingglucuronic acid on side chains, cationized derivatives of guar gum andlocust bean gum, and polyacrylic acid having carboxylic acid.
 15. Thewater based ink having a metallic lustrous color for a ballpoint pen asdescribed in claim 9, wherein the polar solvent is selected from atleast one of the group consisting of ethylene glycol, diethylene glycol,propylene glycol, polyethylene glycol, polypropylene glycol,thiodiglycol, glycerin, diglycerin, 2-pyrrolidone,N-methyl-2-pyrrolidone, dimethylformamide and dimethylimidazolidinone.